A variable discharge fuel pump is utilized to maintain a pressurized fuel supply for a plurality of fuel injectors in a common rail fuel system. For example, U.S. Patent Publication No. 2004/0109768 (the '768 publication) to Sommars et al. teaches a variable discharge high-pressure pump for use in a common rail fuel injection system. In such common rail systems, the pump supplies fuel to the common rail, which in turn supplies the fuel to the injectors when the injectors are energized. The pump serves to maintain the common rail at a desired pressure and does so by associating a pressure driven disk-type shuttle valve with each pump chamber. When one of the pump pistons is undergoing its pumping stroke, the fuel displaced by the piston presses against the shuttle valve to open a passageway allowing fuel to flow to the common rail.
However, because the pump of the '768 publication uses a disk-type shuttle valve, the pump may be expensive and difficult to produce. In particular, the valve seating surfaces that mate with the shuttle valve disk are formed through a time consuming Electrical Discharge Machining (EDM) process, which utilizes expensive manufacturing equipment. The amount of time required to produce the disk-type shuttle valve seating surfaces, in conjunction with expensive EDM manufacturing equipment, can increase the cost of the pump. In addition, high temperatures associated with EDM processes can adversely affect material properties of the shuttle valve surfaces.
Further, because the disk-type shuttle valve relies on surface sealing, tight process tolerances may be required to produce the desired sealing characteristics. These tight process tolerances can further increase the cost of the pump.
The disclosed fuel pump is directed to overcoming one or more of the problems set forth above.